Now you can Root Samsung Galaxy S6 G920F on Official Android 5.1.1 XXU3COI9 Lollipop Firmware.
Follow our guide below to download the update and Root it yourself.

Prerequisites:

•This root method tutorial is only for Galaxy S6 SM-G920F.
•Please do not try on any other Galaxy S6 LTE variants.
•Make sure you backup all your data in your phone before proceeding as a precaution.
•Your Galaxy S6 should be on an official firmware by Samsung, not a custom ROM.Your phone should be on XXU3COI9 Android 5.1.1 firmware.

Disclaimer:
This site or the developers are not
responsible, if you damage or brick your device.Do it on your own risk
and follow the instruction properly.

Step 3 – Switch OFF your phone. Now go to Download Mode. How? Press and
hold the Volume Down + Home buttons together, and then press the Power
button till you see the construction Android robot and a triangle. Press
Power again to confirm to enter into Download Mode.